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Author Topic:   Engine Help, Heads, Cam, Exhaust?
Dirt Full Roller

Total posts: 49
posted May 21, 2002 06:52 AM
I'm builing a SBC 406 for a 1/2 mile, with some runs on a 3/8 mile track. I can't quite come up with the money for Dart heads yet, but this buildup needs to take into account I will upgrade later.
Gearing will be 1/2 = 5.69
3/8 = 6.00
Engine rule:
Cast Heads, Cast intake, Cast exhaust, no roller lifter's, open carb rule, no center dumps on the right side

Car info:Street stock/Hobby stock
1981 Cutlass 3000lbs, ford 9" rearend, 4 wheel disc brake

Here's what I have:
Holley double pump 750 (4779-2) Carb
Intake (14096011) GM Marine cast iron High rise

Head option's I own:
(14014416) 305HO 58cc 1.84/1.5
(376450) 305 1.71/1.5
(333882) 350 76cc 1.94/1.5
(3932441) 350 73cc 1.94/1.5

This is what I thought:
Use the 441 with upgrade to 2.02 valves, runabout 12.5 to 1 compression, then later I can upgrade to Dart 72cc heads with a slight bump in compression. Does this sound close?
What lift and gring of cam would work best?
How about exhaust manifolds? 1 center dump or keep the same type on both sides of the engine?

I want a strong but reliable engine?
Please help.....


Dirt Forum Racer

Total posts: 87
posted May 23, 2002 01:37 AM
Are there any limits on camshaft besides roller lifters? Lift rule? Vacuum rule? The upgraded 441's would be your best head choice of what you've got listed there because they will flow the best on that engine. In regards to manifolds some trucks came with decent manifolds (rear dump) and had larger exhaust pipe flanged up to them. If you could run a center dump on the right side, and if you could find one, the old 60's vettes came with big center dump manifolds. The problem with those is that you might have a better chance of finding a dinosaur tooth in your back yard. They are like gold, especially to the vette guys.

Dirt Full Roller

Total posts: 49
posted May 23, 2002 06:28 AM
Hey BayouGent, thanks for the reply.
The rules are fairly simply Cast,cast,cast, no roller lifters, stock appearing engine.
No center dump on the right side. (1 of the tracks allows centerdumps but the other doesn't on the Right Side.)
I don't understand the no center dump on the Right Side. Not sure what this rule prevents.
There is no lift rule or vacuum Rule at the two tracks I'm thinking of racing.
But they said if you dominate your class, they will pull your distibutor and look for roller lifters.


Dirt Forum Racer

Total posts: 87
posted May 23, 2002 08:37 PM
If you are going to run that much compression, you'll need a good camshaft in that motor. With that gearing I'm guessing that you are wanting to turn the engine 6000-6500 RPM max. The intake you have is perfect because it works from basically off idle to around 7000 rpm. If you aren't planning on spending the money to have your pistons fly cut or are wanting to spend a ton of money on valvetrain keep your max lift in the .500 - .550 range. I suggest having those heads machined for ***** in studs, guide plates, and a set of .600 max lift valve springs that will give you at least 150# of spring seat pressure. See how much money it's going to cost for you to buy new valves plus all of these extras because you might be closer to a set of Dart (World heads are great for the buck too) heads than you think. To keep your powerband fairly broad, you might want to keep your adv. duration (@.050) somewhere in the 250 degree range. Competition cams can run your numbers for you and give you advice on the best cam to buy. A 406 is already a high torque motor, so buying a cam that makes tons of bottom end torque may be overkill. If you're going to be turning around 6500 at the high end of the straights, you want to make sure that your engine will still be making power at that RPM. Just some advice...if your 406 has a stock crank and connecting rods, I haven't seen many that hold up steadily turning over 6000 RPM's, but some people have more luck than others. I recommend a solid cam over a hydraulic, and you definitely want a set of polylocks and long slot rocker arms (get roller rockers if they are in your budget because they just operate so much smoother). As far as the rule for the center dump exhaust manifold, I can't really tell you what it prevents either. I'd get a good set of rear dumps and open em up with a dremmel tool and flange up the largest exhaust pipe I could to it and go from there. Personally I've never tried to run that much motor through a set of manifolds before. The only thing I see the rules testing ya'll with is just how much power you can make without going to a roller cam and lifters and not cooking everything by trying to exhaust through manifolds. Hope this info helps, but I'd try to talk to some of the guys that are racing with the same rulebook to see if you can scrape up any advice from them as well.

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